Question

What are the biggest mistakes you see made by divers?

Answer 1

The biggest mistake I see divers make, is diving beyond their skill and capabilities.  This combination can be deadly. You should always stay within your comfort zone and skill level and never just "Follow the group".

Answer 2

Interesting question. I have a long list from having a friend loaning me a regulator with out a diagram to jumping in without weights. You name it I've probably done it. The scariest is diving into a cave not having a light.